1. Field of the Invention
The present invention relates generally to optical elements, and more particularly to a non-Lambertian diffuser fabricated using mechanical means instead of light and mechanical methods for fabricating the diffuser.
2. Description of the Related Art
Methods for manufacturing and replicating optical components such as a master diffuser exhibiting desired light diffusing characteristics are well known. Many of these methods involve creating a master diffuser by exposing a photoresist material to a source of light and then replicating this master diffuser into one or more submasters of a more durable nature. Many of these methods inherently destroy the master diffuser when creating the submasters. There are also other methods of making replicas of a master diffuser which contain the optical features in the master without destroying the master diffuser. With each of these methods, the master diffuser is initially created optically. Submasters are created from these master diffusers utilizing a number of methods whereby the master diffuser surface is replicated into a submaster surface. These other methods are described in one or more pending U.S. applications, referenced below, which are assigned to the assignee of the present invention.
One such method involves creating a submaster for an optical product by recording optical features on a photosensitive medium using coherent or incoherent light. The photosensitive medium is then further processed to create a master optical product. A layer of two part silicone epoxy is then poured over the master to replicate the optical surface features of the master photosensitive medium in the silicone epoxy material. The silicone epoxy layer cures at room temperature and becomes rubber. The silicone material is then further cured and separated from the master to obtain a silicone rubber submaster. The soft silicone submaster is then used to make successive generations of submasters or final optical products by covering the soft submaster with a layer of epoxy, covering the layer of epoxy with a plastic substrate, curing the epoxy and separating the epoxy and plastic substrate from the submaster. This particular method of creating a diffuser is highly labor intensive, requires use of many different materials, requires performing a number of steps, and must be conducted in a sterile environment.
The specific embodiments described above regarding the rubber submaster and the silver and nickel submaster are disclosed in U.S. application Ser. No. 09/052,586, now U.S. Pat. No. 6,159,398, entitled xe2x80x9cMethod of Making Replicas While Preserving Master,xe2x80x9d commonly assigned to the assignee of the present invention.
Another method of creating a diffuser involves recording optical features in a photosensitive medium using coherent or incoherent light and then processing the medium to create a master. The photosensitive medium is then coated with a layer of silver. A layer of nickel is electroplated onto the silver layer and then the silver layer and layer of nickel are removed from the photosensitive material or medium to form the submaster. The combined silver and nickel backing form a metal shim submaster which is then replicated to fabricate final optical products by embossing the surface features of the submaster into epoxies, plastics or polycarbonate materials, or by injection molding such materials into a mold carrying the submaster. Again, this process is costly, labor intensive, wasteful of material and requires a sterile environment.
Another significant problem with each of these methods is that the submasters or final optical products created from the master optical elements are made from materials such as plastics, epoxies, or polycarbonate composites and exhibit relatively poor long-term characteristics. These materials are also not suited for use near extremely high temperature light sources because they have relatively low melting or softening temperatures when compared to other more durable materials.
Other commonly assigned U.S. patents and pending applications disclose somewhat related methods for making and recording optical products and replicating those products so that they may be mass produced. For example, U.S. Pat. No. 5,365,354 entitled xe2x80x9cGrin Type Diffuser Based on Volume Holographic Material,xe2x80x9d U.S. Pat. No. 5,534,386 entitled xe2x80x9cHomogenizer Formed Using Coherent Light and a Holographic Diffuser,xe2x80x9d and U.S. Pat. No. 5,609,939 entitled xe2x80x9cViewing Screen Formed Using Coherent Light,xe2x80x9d all owned by the present assignee relate to methods for recording and replicating optical products. Each of these U.S. patents is incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.
Related U.S. patent applications include Ser. No. 08/595,307 now U.S. Pat. No. 5,956,106, entitled xe2x80x9cLCD With Light Source Destructuring and Shaping Device,xe2x80x9d Ser. No. 08/601,133, now U.S. Pat. No. 5,838,403, entitled xe2x80x9cLiquid Crystal Display System with Collimated Backlighting and Non-Lambertian Diffusing,xe2x80x9d Ser. No. 08/618,539, now U.S. Pat. No. 5,735,988, entitled xe2x80x9cMethod of Making Liquid Crystal Display System,xe2x80x9d Ser. No. 08/800,872, now U.S. Pat. No. 5,922,238, entitled xe2x80x9cMethod of Making Replicas and Compositions for Use Therewith,xe2x80x9d and Ser. No. 09/075,023 abandoned entitled xe2x80x9cMethod and Apparatus for Making Optical Masters Using Incoherent Light.xe2x80x9d All the above applications are owned by the present assignee and are hereby incorporated by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art. Additionally, each of these patents and applications disclose methods of making optical products wherein the methods or the products exhibit many or all of the above-noted disadvantages.
A primary object of the present invention is to provide a method for making a diffuser optical product utilizing conventional mechanical means instead of the aforementioned holographic and complex and costly methods. Another primary object of the present invention is to provide a diffuser from an extremely durable material such as glass or metal. It is another object of the present invention to provide a diffuser which is suitable for use under extreme temperature conditions such as adjacent a high temperature active light source in a liquid crystal display or the like. It is a further object of the present invention to provide a method for producing such a diffuser which requires fewer steps for creating the diffuser and is less costly in materials, cost of labor and cost of the manufacturing environment.
In accordance with the present invention, these objects are achieved by several methods for producing a diffuser from highly durable materials such as glass or metal and by the resulting diffuser optical products themselves.
In one embodiment, a method for producing such a diffuser first includes providing a substrate body having at least a first side. A working material is then selected which has desired qualities for altering the characteristics of the first side of the substrate body. The working material is applied to the first side in order to form a plurality of irregularities thereon which define a diffuser surface. The diffuser surface exhibits light propagating characteristics defined by the particular characteristics of the plurality of irregularities.
In one embodiment, the working material is a buffing agent having a desired grit. The first side of the substrate body is buffed utilizing the buffing agent which forms a plurality of scratches in the first side according to the particular grit of the agent. The scratches define the diffuser surface and thereby exhibit light propagating characteristics defined by the orientation, contour, length and depth of the plurality of irregularities.
In another embodiment, the working material is an acid or alkali agent selected to react with a particular substrate body material. The acid or alkali agent is placed on the first side of the substrate body for an etching time duration. The acid or alkali agent etches a plurality of irregularities into the first side of the substrate body. The plurality of irregularities each have at least a size, a depth, and a contour formed according to the reaction between the substrate body and the acid or alkali agent as well as etching time duration. The diffuser surface on the first side exhibits light propagation characteristics defined by the size, depth and contour of the irregularities formed by the etching or acid or alkali agent.
In another embodiment, the acid or alkali etching agent also includes a plurality of particles mixed therein each having a size, a shape and a mass. The particles enhance the etching reaction between the substrate body and the acid or alkali agent by forming deeper depressions where the particles are located on the first side of the substrate body. In another embodiment, a pressure may be applied to the first side of the substrate body while the acid or alkali agent and particles are disposed thereon to further enhance penetration of the particles into the first side of the substrate body as the acid or alkali agent reacts with the substrate body material.
In one embodiment, a mask having a plurality of openings formed therein is applied to the first side of the substrate body. The acid or alkali agent is placed on the first side over the mask and thereby etches a plurality of irregularities into the first side where the first side is exposed through the openings of the mask. The irregularities each have a size, depth and contour which are essentially determined by the length, width, orientation and shape of the plurality of openings in the mask as well as the particular reaction between the acid agent and the substrate body as well as the etching time duration.
In one embodiment, the working material is a blasting agent which includes a plurality of shot particles each having a size, a shape and a mass. The blasting agent is forced against the first side of the substrate body such as in a sandblasting operation at a predetermined velocity to form a plurality of irregularities or depressions. The depressions are formed according to the size, shape and mass of the shot particles as well as the predetermined velocity. The diffuser surface structure is defined by the depth, contour and size of the plurality of irregularities formed in the first side of the substrate body.
In another embodiment of the invention, a diffuser is disclosed having a substrate body and at least a first side. A diffuser surface relief structure formed non-holographically in the first side defines a plurality of irregularities therein. The irregularities have light propagating characteristics which are defined by at least one of the size, depth, length, width, orientation, and contour of the plurality of irregularities.
In one embodiment, the substrate body is formed from a glass material substrate. In another embodiment, the substrate body is formed from a hard plastic material substrate. In another embodiment, the substrate body is formed from a metallic material substrate.
In one embodiment, the surface relief structure is comprised of a plurality of scratches formed by buffing the first side with a buffing agent having a predetermined grit. In another embodiment, the surface relief structure is comprised of a plurality of closely spaced depressions in the first side formed by forcing a plurality of shot particles at a predetermined velocity against the first side. In a further embodiment, the surface relief structure is acid etched into the first side by an acid agent placed on the first side of the substrate body.
These and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof and the invention includes all such modifications.